WISC-IV (Wechsler Intelligence Scale for Children) is an IQ test used with children ages
6-16. Like other IQ Tests, the WISC-IV is
designed to measure skills and abilities, rather than grade-level subject
knowledge. It can be given to both readers and non-readers as it is both
verbal and visual. Within the WISC there are four categories of subtests: Verbal
Comprehension, Perceptual Reasoning, Working Memory, and Processing Speed.
The problem
with using the WISC-IV to test some students is that sometimes the Full Scale
IQ scores are excessively lowered by their Working Memory and Processing Speed
scores, when averaging out the scores from all the subtests. This is unfortunate
for gifted students, Dyslexic and Dysgraphic students, and gifted Dyslexics,
all of whom may do poorly on Working Memory and Processing Speed.
In
an attempt to provide an alternative to this test, the General Ability Index
(GAI) was implemented, which provides an IQ score derived only from the Verbal Comprehension
and Perceptual Comprehension indices of the test.
When there is
a statistically significant difference between one's Verbal Comprehension and
Perceptual Reasoning IQ Scores, and their Working Memory and Processing Speed
scores, the GAI can be calculated and reported as a representation of cognitive
ability, without the influence of Working Memory and Processing Speed. This score is important because it highlights certain
aspects of cognitive ability necessary for advanced or gifted placement. Thus,
schools often use this score to place children in different classes (e.g.,
gifted or special ed.) or to predict future academic success. Processing
Speed and Working Memory are both important areas of one's cognitive
proficiency, however the GAI gives psychologist's an alternative method of
reporting "intelligence" when these areas are weaker for many due to
a variety of reasons.
The full
scale IQ (FSIQ) score should not be reported if the variance from the highest
to the lowest composite score is 23 or more points and if the Verbal
Comprehension and Perceptual Reasoning Indices vary by less than 23 points. In
this case, the GAI should be used instead.
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diagnostic learning center.
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